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Subject: Re: Opening book

Author: Frank Phillips

Date: 22:46:39 04/03/99

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On April 01, 1999 at 15:56:14, Andrew Williams wrote:

>On April 01, 1999 at 14:37:51, Frank Phillips wrote:
>
>>I have added an opening book to my developing program and am wondering about
>>better ways of storing the information.  At the moment I store opening positions
>>as a hash-table in a disk file, accessing them as I would a hash table stored in
>>RAM by shifting the hash code for  the appropriate number of places to generate
>>the index and then performing a lookup as
>>fseek(pfile,index*sizeof(record),SEEK_SET)  etc.  This works but involves a lot
>>of wasted storage.  For example, I have a 12MB file of about 1million records
>>with the order of only 100 000 book entries.  Is it normal having generated the
>>book to then sort and search it as a simple linear file instead?  What do others
>>do?
>
>In my program, I don't store blank entries. I simply store the entries that
>exist and do a binary search on the file to see if the position is in the
>book. The hash key is the same as the one used in the transposition table,
>but I use it in a different way.
>
>Andrew

Thanks.    I eventually used a quick sort function found on the internet which
seems to work fine. As expected, my book size is now about a tenth of the one
storing mainly zero.  There is also no noticeable, practical difference in speed
of accessing via binary search compared to hashing.


Initially I tried the MSVC 5 qsort() library function but could not work out how
to use the  (compare) function with structures.

qsort((void*) precord, records, sizeof(BookHashRecordT), compare);

int __cdecl compare( const void *a, const void *b )
{
/*  The thing I want to sort on is in record.top32bits, where record is of type
BookHashRecordT. */

return( );
}

(precord is a pointer to the memory area storing the records.  records the
number of records.).

If anybody can enlighten me I would be interested.




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